The embodiment of the present invention relates to a liquid crystal display (LCD) backlight module.
A backlight module is a device for converting a linear light source into a surface light source with high brightness and high uniformity. A conventional LCD backlight module is shown in FIGS. 1A and 1B, for example. The backlight module comprises a bottom reflection plate 10, a light guide plate 11 on the bottom reflection plate 10 to convert a linear light source into a surface light source, an upper diffusion sheet 15 and a lower diffuse plate 12 to diffuse the light from the light guide plate 11, an upper prism sheet 14 and a lower prism sheet 13 to condense the light from the lower diffuse plate 12, a light source 16 disposed on both sides of the light guide plate 11, and a backlight reflection plate 17 enclosing the light source 16 to reflect the light back into the light guide plate 11.
In operation of the LCD, the light emitted from the light source 16 such as a cold cathode fluorescence light (CCFL) is reflected back into the light guide plate 11 by the backlight reflection plate 17 to form a surface light source applicable for the LCD. The reflection plate 17 is typically in a “C” shape in cross-section enclosing the light source 16 to reflect the light into the light guide plate 11, as shown in FIG. 2. FIG. 3 is a cross-sectional view taken along line A-A in FIG. 2. As shown in FIG. 3, the sectional shape of the reflection plate 17 is a rectangle with a uniform thickness. The reflectivity of the backlight reflection plate 17 is uniform throughout the plate.
When a CCFL is used as the light source for the backlight module, there is a brightness difference between a positive electrode and a negative electrode at the opposing ends of the CCFL. FIG. 4 is a schematic view showing a simulation of brightness value distribution on a LCD panel using a CCFL as the light source with a positive electrode 2 and a negative electrode 3, in which the brightness value in a specific box is an average value within the box. As shown in FIG. 4, the brightness value at a region close to the positive electrode 2 of the light source is higher than the brightness value at a region close to the negative electrode 3 of the light source, which adversely affects display quality of the LCD.